I think it's the heat. At the ripe old age of 17 I took the front wheels off my 1966 Mustang GT fastback and replaced them w/ some smaller ones just to see if it handled any better. Took it out on the highway and ran it up through the gears to 135 MPH, where it topped out. Slowed it down and got off the highway, then tore threw some curves sideways at 90 to get a feel of things.
I turned onto the road that led to the house, and suddenly the steering wheel started violently thrashing back and forth in my hands, so I had to creep into the front yard at 5 MPH. When I looked at the front wheels they were at an odd angle. I put a jack under the car, took off one hubcap, and three lug nuts fell out on the ground. Went to the other side, took the hub cap off, and FOUR lug nuts fell out. The remaining three lug nuts that were holding on the two front tires were holding on by just one thread.
Seems that when I changed the wheels I had put the lug nuts on snug by hand, thinking to tighten them down w/ the lug wrench after the car had been lowered to the ground. But I had forgotten to cinch them up w/ the wrench, and popped the hubcaps back on anyway. It was in the South, and about 100 degrees out if I remember correctly.